The N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide-catalyzed (Me3SiNTf2-catalyzed) group transfer polymerization (GTP) of methyl methacrylate (MMA) has been studied for synthesizing stereospecific star-shaped poly(methyl methacrylate)s (PMMAs). The catalytic property of Me3SiNTf2 for the GTP of MMA using 1-methoxy-1-trimethylsilyloxy-2-methyl-propene as the initiator was confirmed by a kinetic investigation and matrix-assisted laser desorption ionization time-of-flight mass spectrometry measurement. The initiating efficiency (f) of Me3SiNTf2 was 0.941.00, which was estimated by the value of Mn(calcd)/Mn(SEC). The Me3SiNTf2-catalyzed GTP of MMA was carried out using initiators possessing three, four, and six MTS groups (MTS3, MTS4, and MTS6, respectively) under the condition of [MMA]0/[MTS3, MTS4, or MTS6]0 = 120 at -55 degrees C. All the obtained PMMAs exhibited unimodal and narrow molecular weight distributions as Mw/Mns = 1.031.04 and the Mw(MALS)s of the 3-, 4-, and 6-armed star-shaped PMMAs (PMMA3, PMMA4, and PMMA6, respectively) were 12.9, 12.9, and 13.4 kgmol-1, respectively, which fairly agreed with the calculated Mw(calcd) values. The syndiotacticities, rrs, of PMMA3, PMMA4, and PMMA6 were in the range of 8789%. The stereoblock synthesis of PMMA3, PMMA4, and PMMA6 was performed by the first and second polymerizations at -55 and 45 degrees C; the rrs of the first and second PMMA blocks were 87.0, 87.0, and 86.0% and 65.0, 65.0, and 64.0%, respectively. The glass transition temperatures (Tgs) were 118.1, 115.8, and 111.5 degrees C for the respective syndiotactic-rich PMMA3, PMMA4, and PMMA6 and 111.5, 109.7, and 107.6 degrees C for the respective stereoblock ones. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012